Mcclain reel mower problem?

I am having problems with my pull sting on my Mcclain reel mower. It has a 3 hp Briggs and Stratton engine on it. When you pull out the sting to start the mower it starts right up. The sting winds itself back up like normal but after using the mower for a few min the mower makes a loud screeching noise. It looks like the sting somehow is getting unwound inside the cover or something. If I pull the sting to start the mower and don’t let it wind back up the mower will not make the noise. Has anyone had this problem or any idea how to fix it? Thanks